1. Field
The present disclosure relates to a clamping apparatus and method for clamping a workpiece during processing.
2. Background of the Disclosure
In the area of semiconductor chip packaging, an example process for attaching a semiconductor chip module to another device includes joining a heat spreader to a joined die which includes a laminate and a die. After a heating process to bond or attach the heat spreader to the joined structure by attaching the heat spreader to the laminate, the substrate or laminate is susceptible to warping during and after the process. For example, the laminate material can warp when cooling from a cure temperature. Warping is undesirable because it can lead to die cracking, thermal interface material (TIM) tearing, and ball grid array (BGA) coplanarity failure. All of which are unacceptable in meeting chip quality control standards.
Undesirable die stresses can also result from variations in the laminate shape during processes which require heating, such as during processing of a chip/die and a laminate, for example, during bonding of a component to a die or module as discussed above. Die stresses can manifest themselves as a cracked die, or separations of the dielectric layers within the die (e.g., typically, white bumps). Increased laminate warpage (also referred to as warping) can also lead to increased module warpage at the end of a bond and assembly process, which can cause the module to fail final co-planarity specifications. Thus, substrate or laminate warpage is undesirable as discussed above.
Laminate warpage or warping may be defined by the laminate's curvature from a flat surface of the bottom of the laminate. Alternatively, laminate warpage may be defined by a planar surface mating with the bottom of the laminate, thereby providing a horizontal plane to reference any warping of the laminate.
Bottom surface metallurgy (BSM) (for example, including an array of copper pads) warpage for land grid array (LGA) (for example, surface mount packaging for integrated circuits) is desirably minimized for achieving optimal electrical contact when a module is connected to a card or board.
For example, a heat spreader may be attached to a joined chip to achieve an increased thermal performance of a chip. A force applied to a heat spreader in a heat spreader attach operation may also bend the laminate of the joined die, flipping the edges upward and changing the overall shape of the BSM. This change of shape increases a BSM warpage value. The processed module may have a warpage specification. Thus, warpage of the BSM caused by laminate warping can have undesirable consequences in meeting specification for a module.
Referring to FIGS. 1-3, an example embodiment of a prior art joining process and joining device (also can be referred to as a clamping fixture) for applying a force to a joined die and heat spreader during processing is discussed below. The joining process shown in FIGS. 1-3 includes using a joining device including a base 10 having opposing support walls 12 extending upwardly from the base and defining a work area 14. The work area is designed to accept a joined die having a laminate 20 and a die 24 over the laminate. A joined die includes a laminate 20 having distal ends 22 which are turned downwardly. A die 24 is attached to the laminate 20.
Referring to FIG. 2, alignment members 30 are positioned over the support walls 12. A thermal interface material (TIM) 34 is layered over the top of the die 24. Structural adhesive patches 38 are positioned on the laminate. As shown in FIG. 3, a heat spreader 40 is positioned over the joined die such that legs 42 of the heat spreader contact the structural adhesive patches 38. A plate 50 includes a spring 54, and is placed over the base and joined die and heat spreader such that the spring contacts the heat spreader.
During a curing process to join the heat spreader 40 to the die and laminate, pressure 60 (that is, a force) is applied to the plate 50. The pressure 60 assists in successfully joining the heat spreader to the die and laminate. However, the ends 22 of the laminate are turned (or flipped) upwardly. This turning or flipping of the laminate is undesirable as the laminate is preferred to be substantially planar for attaching the laminate and thus the joined die to a circuit board or the like.